Blender not saving changes to object's origin point
It sounds like you accidentally added a keyframe to your object. So even if you move it, it will snap back to the keyframe position. You can fix this by opening the NLA editor and deleting all animation on your cube, or opening the Dope Sheet and deleting the keyframe you don't want. A common way to add keyframes by accident is by pressing the Auto Keyframe button (at  the bottom of the timeline), this causes any rotation, scale, or movement to your object to be keyframed.


You can acsess the Dope Sheet through this menu:


Once in the Dope Sheet, select the keyframes you don't want and press delete.